Sorry to disappoint you, but he wasn't actually born in a dump, and his real name isn't actually Maniac. It's Jeffrey Lionel Magee.
How does Jeffrey Lionel become Maniac? It begins with a tragic trolley crash that kills both his parents when he is three.
Jeffrey doesn't immediately take off on his own—first, he goes to live with his Aunt Dot and Uncle Dan in Hollidaysburg, Pennsylvania.
Losing both your parents and going to live with your aunt and uncle would be hard no matter what, but Uncle Dan and Aunt Dot make it considerably harder.
See, they're serious Catholics, and that makes divorce a dirty word.
Did we mention that they hate each other?
For eight years, Jeffrey lives with his aunt and uncle and two of everything (toasters, bathrooms, TVs, refrigerators) so that his aunt and uncle don't have to see each other more than absolutely necessary.
If you're thinking that sounds like no way to live, you're absolutely right. And during the spring musicale when Jeffrey is 11, he finally has enough.
Spying Aunt Dot and Uncle Dan sitting on opposite sides of the auditorium, Jeffrey loses it and starts to scream (in other words, he goes ahead and does what we've all wished we could at one point or another).
After the "birth scream of a legend" (1.12) Jeffrey starts running, "never again to return to the house of two toasters. Never again to return to school" (1.14).